1,2,3 blocks..........89.5 degrees

[Terrywerm]

I never use digital calipers or the like. They only read to 1/2 thou. A good dial caliper can be read to 1/4 thou by eye,and I like that better. Even if it's NOT really accurate to 1/4 thou,as long as you use the same caliper for all the parts,things work out.

Not to mention that the batteries never go dead on you at the worst time either. Can you tell that I am a fan of good dial calipers too? I have a digital caliper that I never use. It was a cheap one, but is quite accurate. Problem is that it eats batteries like crazy.

Back to the original subject of this thread: I also would suspect the digital protractor first. Most of them are not very accurate. I have had a couple of them, found out neither one was really any good, and they have both gone to that big toolbox in the sky. I seriously doubt that I will ever buy another one, either. It is just as easy to use a sine bar for those accurate angle measurements.

 

[Building Something]

Thanks for the info. Looks like it's probably the protractor. Today I do not have anything to check square (except perhaps my 1,2,3 blocks) A couple years back I sold a set of small engineer squares and a Starrett combo square. I sold a bunch of stuff that I wish I had back (it seemed like a good idea at the time to lighten my load). I was a finish carpenter who dreamed of precision......but there is no real need for anything better than 1/32. Non-Machinists don't see gaps in wood that small. Actually it's amazing what people will ignore. An old Carpentry addage is, "the nicer you make it the more problems they will see"................ahhhh I hate that addage. Anyway, I've found a whole new world of precision ).

Sounds like there isn't an accurate option out there for a digital protractor.....

 

[GaryK]

I assume that you have at least two 123 blocks. To check them I would use a surface plate and stand two of them on end and slide them together. You shouldn't be able to see light between them.
If you see light at either the top or bottom at least one of them is not square. Rotate one of them around or flip it upside down and check again.

Keep repositioning the blocks and check again and you can probably determine where they are out of square.

You can also hold the two blocks together and check the with a straight edge along both surfaces. Once again you should see no light between the straight edge and either block.

 

[darkzero]

Sounds like there isn't an accurate option out there for a digital protractor.....

There are but they're pretty expensive!


I have an import (SPI) that I scored on ebay for $95 new, $263 @ Enco.



I have no idea how great it's accuracy is but it more than good enough for me. Here it is measuring a pair of cheap 1-2-3s after calibrating the protractor with the square it comes with.





And the other one.





Measuring a really cheap square, which reminds me that I been needing to replace it.





Measuring a Mitu combo square.



Probably just a coincidence that the reading is so low on the Mitu. I'm thinking it won't read that again if moved, I'll check it's repeatability some other time.

 

[Building Something]

I hope I'm not responding and duplicating all the pictures..........as worthy of duplication as they are! I've got to keep my eye out for a similar deal on a real digital protractor as you have here. Thanks for the info. I need to get a few basic measuring tools, starting with a granite slab, a digital protractor etc. and learn how to use them. The Sine bar mentioned looks like a powerful tool, but a bit complicated, maybe its easier to understand hands on. I'll be making chips in no time! Maybe even accurately.

I wish there was some way for me to learn this stuff hands on.


I have an import (SPI) that I scored on ebay for $95 new, $263 @ Enco.



I have no idea how great it's accuracy is but it more than good enough for me. Here it is measuring a pair of cheap 1-2-3s after calibrating the protractor with the square it comes with.





And the other one.





Measuring a really cheap square, which reminds me that I been needing to replace it.





Measuring a Mitu combo square.



Probably just a coincidence that the reading is so low on the Mitu. I'm thinking it won't read that again if moved, I'll check it's repeatability some other time.[/QUOTE]

 

[Kevin45]

If you have some Prussian Blue, check one block against the other. Blue up one side of the 3" side of your block, then slide the other against it and rub it ever so slightly back and forth, making VERY sure you stay seated on the 1" side against the surface plate. Then using the same block with bluing, blue up the opposite side and check it against the opposite side of the unblued block. If one or both blocks are not ground square, you will see a void at the top of one side of the 3" surface, and will see a void at the bottom of the opposite side of the same block. If you find that they are NOT square, about the only thing you can do is "A"- send them back for a refund or replacement, or "B"- Grind the two blocks square, keep them as a matched set, and never use them for a 1"-2"-3" precision block. At least they would be square although undersized.